Radiation controlled electron radiation source



Dec. 20, 1966 A. ENGEL 3,293,483-

RADIATION CONTROLLED ELECTRON RADIATION SOURCE Filed Jan. 8, 1962 2Sheets-Sheet 1 Jnvenfar:

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Dec. 20, 1966 A. ENGEL 3,293,483

RADIATION CONTROLLED ELECTRON RADIATION SOURCE 2 Sheets-Sheet 2 FiledJan. 8, 1962 WILD-.7111. B

a o. W in I'm/M15115 United States Patent D 3,293,483 RADIATIONCONTROLLED ELECTRON RADIATION SOURCE Albrecht Engel,Berlin-Siemensstadt, Germany, assignmto Siemens & HalskeAkticngesellscliaft Berlin and Munich, a corporation of Germany FiledJan. 8, 1962, Ser. No. 164,673 13 Claims. (Cl. 315-40) The inventiondisclosed herein is concerned with an electron radiation or electronbeam source, comprising an adjusting element or member with variableresistance, such element being disposed in the lead extending to thecathode and permitting the regulation of the power and the focusing ofthe electron beam emitted from the radiation source, by alteration ofthe cathode potential which is positive with respect to the potential ofthe control diaphragm.

The various objects and features of the invention will appear from thedescription of embodiments thereof which is rendered below withreference to the accompanying drawing.

The electron beam source is schematically indicated in the upper portionof the drawing. The cathode K which is supplied with heating voltagefrom the transformer T has a potential which is positive with respect tothe potential of the control diaphragm S, since there is an adjustingelement inserted in the lead extending to the terminals carrying theacceleration volt-age U such adjusting element being shown in the formof a resistor W1 at which a voltage drop appears in operation. The poweras well as the focusing of the electron beam which leaves the electronbeam source proper, comprising the cathode K, the control diaphragm Sand the anode A (shown within the dot-dash rectangle), can be regulatedby alteration of the resistance value of the adjusting element W1, whichmay be effected, for example, mechanically.

Difiiculties are experienced in connection with this known arrangementowing to the necessity of providing, in view of the very highacceleration voltage U very good insulation for the actuating meansrequired for the adjustment of the resistance value of the adjustingmember Wl. The use of a diode as an adjusting member W1, in place of theresistor indicated in the drawing, will necessitate an auxiliarytransformer for the supply of the heating voltage of the diode andtherewith for the adjustment of its saturation current, and saidtransformer must be constructed as an insulation alternator in view ofthe high acceleration voltage U The requirement for a reliableinsulation of all actuation means entails costly and extensiveconstructions.

Another disadvantage results from the nature of the mechanical actuationof the adjusting member in a case in which the equipment which deliversthe high tension voltage serving as an acceleration voltage, is providedwithin a closed pressure vessel. It is for example necessary to disposein such case the drive motor for the adjusting element within thepressure vessel, so as to obtain the required tightness, and such vesselmust be of correspondingly large size or must be provided with tightlyscaling lead-through means for the movable parts.

The problem underlying the invention resides in providing an arrangementwhich avoids these and other disadvantages and drawbacks of the knownelectron radiation sources.

The invention solves this problem by the provision of an electron beamradiation source comprising an adjusting element the resistance value ofwhich can be varied by incident radiation, that is, a radiationsensitive adjusting element, preferably a cadmium sulphide resisice tor,and having, moreover, devices for producing the incident radiation aswell as for the alteration of the values which characterize the incidentradiation and which affect the resistance value of the radiationsensitive adjusting element.

Visible radiation such as is produced by light sources, can be utilizedin many cases to serve as incident radiation. It is, however, alsopossible to use for this purpose invisible radiation, for example, heatradiation.

The above described diificulties, occasioned by the mechanical actuationof the known adjusting means, are avoided, owing to the fact that theadjusting element is actuated without mass, that is, that the actuationdoes not require mechanical actuating means.

In the drawings, wherein like reference characters indicate like orcorresponding parts:

FIG. 1 is a diagrammatic figure of an electron radiation sourceembodying the invention; and

FIG. 2 is a diagrammatic figure, similar to FIG. 1, illustrating amodified form of the invention.

Referring to FIG. 1, the radiation sensitive adjusting element W1 isrepresented as a resistor. This adjusting element is irradiated by theradiation b which is produced by the radiation source L. The resistanceof the adjusting element and therewith the potential difference betweenthe cathode and the control diaphragm will be of different magnitude,depending upon the intensity of this radiation and the size of theirradiated area. The same effect can in many cases be produced byalteration of the spectral composition of the radiation b, since theelements employed as radiation sensitive adjusting members frequentlyexhibit a frequency dependence of the resistance value thereof.

A regulation of the resistance value of the adjusting member mayaccordingly be effetced, for example, by altering the intensity of theincident radiation 1) with respect to a constant irradiated area of theadjusting member W1. The drawing indicates several possibilities towardthis end.

For example, the voltage U supplied preferably from a commercialnetwork, can be conducted to the radiation source L over a regulatablevoltage divider W2, so that the voltage for the radiation source isadjustable. It is clear, of course, that other devices, for example, aregulatable transformer, may be used for this purpose in place of theregulatable voltage divider.

Another possibility for varying the intensity of the incident radiationresides in using gray filters F in the radiation path which holding thevoltage constant.

Upon using color filters in place of gray filters F, the spectralcomposition of the radiation directed to the radiation sensitiveadjusting member W1 will be varied, thus likewise effecting variation ofthe resistance value thereof.

It is also possible to vary instead of the intensity or the spectralcomposition of the radiation, as the value which characterizes theincident radiation, the cross-sectional size of the incident radiationand therewith the size of the irradiated area of the radiation sensitiveadjusting member. One or more, preferably continuously adjustablediaphragms such as the diaphragm B may be used for this purpose, suchdiaphragm or diaphragms defining only a small angle from the entireradiation range of the radiation source.

It is of course understood that the various measures for the regulationof the resistance value of the adjusting member W1 may be employed incombination, as indicated in the drawing.

The switching elements used for the adjusting member are generally onlyin a limited sense voltage resistant, and light electrical resistorshaving considerable inertia,

that is, they require considerable time for assuming responsive toirradiation a resistance value lowered from an initially higher value,and it is therefore advantageous to construct the adjusting member of aplurality of serially successively arranged switching elements. ThisWill make it possible to place the characteristic working point of theindividual switching elements within a range of sufiiciently lowinertia. The different elements of the adjusting member, so far as theresistance value thereof is concerned, can be regulated by incidentradiation emanating from a single radiation source. However, it may beof advantage, with a view of finer regulation of the resistance value ofthe adjusting member, to allocate to each element thereof a separateradiation source.

The advantages of the electron radiation source according to theinvention become particularly apparent upon use thereof in connectionwith the previously noted case in which the adjusting member togetherwith the means for producing the acceleration voltage are disposedwithin a closed pressure vessel. The dimensioning of the pressure vesselbecomes practically independent of the radiation sensitive adjustingmember since there are no mechanical actuating means that have to beconsidered and since the radiation which constitutes the actuating meanscan in simple manner be passed through a suitable window formed in awall of the pressure vessel.

FIG. 2 illustrates the use of two switching elements for the adjustingmember W1, which are enclosed in a pressure vessel D which would containthe means for producing the acceleration voltage. The vessel D isprovided with a sealed window G, which is aligned with the elements ofW1 and the radiation source L, whereby radiation from the latter may bedirected through the window upon the elements of W1.

The amount of radiation striking the elements of W1 may be controlled byany one or combination of the regulating possibilities discussed withreference to FIG. 1, such as the adjustable voltage divider W2, grey orcolored filters F, and one or more diaphragms B. The combination of theadjusting member, radiation source and means for controlling theoperation of the radiation source with respect to the adjusting member,thereby controlling the operation of the latter, provides a unitary orself-contained control device that eliminates the disadvantages of theprior known arrangements.

Changes may be made within the scope .and spirit of the appended claimswhich define what is believed to be new and desired to have protected byLetters Patent.

Iol-aim:

1. An electron radiation source comprising the combination of a cathodeand a control diaphragm, an adjusting member with variable resistancevalue disposed in a lead extending to the cathode, said adjusting membereffecting by alteration of the potential of the cathode, which ispositive with respect to the potential of the control diaphragm, controlof the power and of the focusing of the electron beam emitted from thecathode, said adjusting member being sensitive to radiation whereby theresistance thereof is variable responsive to incident radiation directedthereagainst, means, associated with and forming a part of said source,for respectively producing the incident radiation and means, likewiseassociated with and forming a part of said source, for altering thevalues which characterize the incident radiation and thereby affect theresistance value of the radiation sensitive adjusting member.

2. An electron radiation source according to claim 1, wherein a cadmiumsulphide resistor constitutes said adjusting member.

3. An electron radiation source according to claim 1, wherein saidincident radiation is a visible radiation produced with the aid of alight source.

4. An electron radiation source according to claim 3, comprising avoltage source for supplying current to said light source, circuit meansfor connecting said voltage source to said light source, and aregulatable voltage divider included in said circuit means for varyingthe in tensity of said incident radiation which is applied forirradiating a defined area of said radiation sensitive adjusting member.

5. An electron radiation source according to claim 3, comprising grayfilter means for varying the intensity of said incident radiation whichis applied for irradiating a defined area of said radiation sensitiveadjusting memher.

6. An electron radiation source according to claim 3, comprising colorfilter means for varying the spectral composition of said incidentradiation which is applied for irradiating a defined area of saidradiation sensitive adjusting member.

7. An electron radiation source according to claim 1, wherein saidincident radiation is of constant intensity and spectral composition,comprising control means for varying the cross-sectional area of saidincident radiation and therewith the area of irradiation of saidradiation sensitive member.

8. An electron radiation source according to claim 1, wherein saidincident radiation is of constant intensity and spectral composition,comprising continuously adjustable diaphragm means for varying thecross-sectional area of said incident radiation and therewith the areaof irradiation of said radiation sensitive member.

9. An electron radiation source according to claim 1, comprising controlmeans for respectively varying parameters which affect the operation ofsaid radiation sens-itive adjusting member, said parameters includingthe intensity and spectral composition of said incident radiation andthe area of the adjusting member which is being irradiated.

10. An electron radiation source according to claim 1, wherein saidadjusting member is composed of a plurality of serially connectedradiation sensitive elements.

11. An electron radiation source according to claim 1, wherein saidradiation sensitive member is composed of a plurality of seriallyconnected cadmium sulphide resistors.

12. An electron radiation source according to claim 1, wherein saidradiation sensitive member is composed of a plurality of cadmiumsulphide resistors, and a source individual to each resistor forproducing the radiation energy thereof.

13. An electron radiation source according to claim 1, in combinationwith a device for producing a high tension volt-age serving as anacceleration voltage, said device and said radiation sensitive adjustingmember being enclosed within a pressure vessel, and a window formed in awall of said vessel through which said incident radiation is directedfor the irradiation of said adjusting member.

References Cited by the Examiner UNITED STATES PATENTS 2,289,914 7/1942Kell 315-30 2,786,960 3/1957 Palmer 31510 2,924,743 2/1960 McN'aney315-10 3,025,345 3/1962 Suhrmann 315-10 3,087,069 4/1963Moncriefif-Yeates 250-21l.2

FOREIGN PATENTS 223,728 9/1958 Australia.

1,03 0,428 5/ 1958 Germany.

OTHER REFERENCES Zworykin et al., Electron 0 Ties and the ElectronMicroscope, Wiley and Sons, Inc, New York, 1945, pp. 23 8239.

DAVID G. REDINBAUGH, Primary Examiner.

ROY LAKE, Examiner. I. E. BECK, T. A. GALLAGHER, Assistant Examiners.

1. AN ELECTRON RADIATION SOURCE COMPRISING THE COMBNATION OF A CATHODEAND A CONTROL DIAPHRAGM, AN ADJUSTING MEMBER WITH VARIABLE RESISTANCEVALUE DISPOSED IN A LEAD EXTENDING TO THE CATHODE, SAID ADJUSTING MEMBEREFFECTING BY ALTERATION OF THE POTENTIAL OF THE CATHODE, WHICH ISPOSITIVE WITH RESPECT TO THE POTENTIAL OF THE CONTROL DIAPHRAGM, CONTROLOF THE POWER AND OF THE FOCUSING OF THE ELECTRON BEAM EMITTED FRM THECATHODE, SAID ADJUSTING MEMBER BEING SENSITIVE TO RADIATION WHEREBY THERESISTANCE THEREOF IS VARIABLE RESPONSIVE TO INCIDENT RADIATION DIRECTEDTHEREAGAINST, MEANS, ASSOCIATED WITH AND FORMING A PART OF SAID SOURCE,FOR RESPECTIVELY PRODUCING THE INCIDENT RADIATION AND MEANS, LIKEWISEASSOCIATED WITH AND FORMING A PART OF SAID SOURCE, FOR ALTERING THEVALUES WHICH CHARACTERIZE THE INCIDENT RADIATION AND THEREBY AFFECT THERESISTANCE VALUE OF THE RADIATION SENSITIVE ADJUSTING MEMBER.